In Exercises 1–26, find the exact value of each expression. _ tan⁻¹ √3/3
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- 0. Review of College Algebra4h 45m
- 1. Measuring Angles40m
- 2. Trigonometric Functions on Right Triangles2h 5m
- 3. Unit Circle1h 19m
- 4. Graphing Trigonometric Functions1h 19m
- 5. Inverse Trigonometric Functions and Basic Trigonometric Equations1h 41m
- 6. Trigonometric Identities and More Equations2h 34m
- 7. Non-Right Triangles1h 38m
- 8. Vectors2h 25m
- 9. Polar Equations2h 5m
- 10. Parametric Equations1h 6m
- 11. Graphing Complex Numbers1h 7m
5. Inverse Trigonometric Functions and Basic Trigonometric Equations
Inverse Sine, Cosine, & Tangent
Problem 23
Textbook Question
In Exercises 1–26, find the exact value of each expression. _ csc⁻¹ (− 2√3/3)
Verified step by step guidance1
Recall that the function \( \csc^{-1}(x) \) is the inverse cosecant function, which gives an angle \( \theta \) such that \( \csc(\theta) = x \). Our goal is to find \( \theta \) where \( \csc(\theta) = -\frac{2\sqrt{3}}{3} \).
Use the identity relating cosecant and sine: \( \csc(\theta) = \frac{1}{\sin(\theta)} \). Therefore, \( \sin(\theta) = \frac{1}{\csc(\theta)} = \frac{1}{-\frac{2\sqrt{3}}{3}} = -\frac{3}{2\sqrt{3}} \).
Simplify the expression for \( \sin(\theta) \) by rationalizing the denominator: multiply numerator and denominator by \( \sqrt{3} \) to get \( \sin(\theta) = -\frac{3\sqrt{3}}{2 \times 3} = -\frac{\sqrt{3}}{2} \).
Determine the angle \( \theta \) whose sine is \( -\frac{\sqrt{3}}{2} \). Recall that \( \sin(\theta) = \pm \frac{\sqrt{3}}{2} \) corresponds to reference angles of \( \frac{\pi}{3} \) (or 60 degrees). Since the sine is negative, \( \theta \) must be in either the third or fourth quadrant.
Identify the principal value range for \( \csc^{-1}(x) \), which is usually \( [-\frac{\pi}{2}, 0) \cup (0, \frac{\pi}{2}] \) excluding zero. Find the angle \( \theta \) in this range with \( \sin(\theta) = -\frac{\sqrt{3}}{2} \).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Inverse Cosecant Function (csc⁻¹)
The inverse cosecant function, csc⁻¹(x), returns the angle whose cosecant is x. It is the inverse of the cosecant function, which is defined as csc(θ) = 1/sin(θ). Understanding its domain and range is essential to find the correct angle corresponding to a given value.
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Relationship Between Cosecant and Sine
Cosecant is the reciprocal of sine, so csc(θ) = 1/sin(θ). To find an angle from a cosecant value, first find the sine value by taking the reciprocal. This relationship helps convert the problem into finding an angle from a sine value, which is more straightforward.
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Graphs of Secant and Cosecant Functions
Exact Values of Special Angles
Certain angles have well-known exact sine and cosecant values, often involving √2, √3, and rational numbers. Recognizing these special angles (like 30°, 45°, 60° or π/6, π/4, π/3) allows you to identify the angle corresponding to the given cosecant value without a calculator.
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